⚗[RUMF-1079] add lock mechanism for session cookie writes

[bcaudan]

Motivation

Mitigate session inconsistencies due to concurrent access to cookies by different tabs (chromium browsers).

Changes

• introduce a sessionCookieStore for session cookie methods
• introduce an API to write into session cookie protected by lock
• lock mechanism enabled by flag cookie-lock

Testing

• Local
• Staging
• Unit
• End to end

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I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Merging #1230 (d275211) into main (65dd3a1) will increase coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1230      +/-   ##
==========================================
+ Coverage   89.13%   89.29%   +0.15%     
==========================================
  Files         104      105       +1     
  Lines        4254     4317      +63     
  Branches      962      979      +17     
==========================================
+ Hits         3792     3855      +63     
  Misses        462      462              

Impacted Files	Coverage Δ
...ges/core/src/domain/session/oldCookiesMigration.ts	100.00% <ø> (ø)
...ages/core/src/domain/session/sessionCookieStore.ts	100.00% <100.00%> (ø)
packages/core/src/domain/session/sessionStore.ts	100.00% <100.00%> (ø)

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